ABS light is on, speedometer not working, and not shifting
 

My brother called me and told me that his 1999 Blazer's ABS light is on, speedometer not working, and is not shifting. I can't pull any codes cause he doesn't live close by, so I've looked up this problem on the net and found that it could be the speed sensor? The problem is that when I went to look up the part, I found that this vehicle has like 3 different speed sensors? The VSS, the ABS speed sensor, and the ABS wheel speed sensor...which one should he change? His fuse box that's located under the hood doesn't have it's cover on, and it's been raining, I told him to check each fuse t see if maybe the fuses got wet and blew somehow. Is it possible for the under the hood fuses to get wet without it's cover on when it rains?

VSS controls the speedo and interacts with the ABS system.

i changed the vss on mine. That solved my issue. It had the same described problem.$30 at autozone.'01 4wd with the thread in type.

Would a bad brake booster cause problems for the ABS, and in turn mess with the VSS?

Shouldn't. The VSS is electronic and has nothing really to do with the braking system other than it is one of the sensors that feeds info to the ABS controls.

My brother took his Blazer to Pep Boys, and supposedly they checked the VSS and found nothing wrong with it, and they couldn't do any further tests because the brake booster is bad. So, if it's not the VSS, what else could it be? Or, could the VSS still be bad, and whatever test they performed didn't pick it up?
The Blazer isn't shifting from 1st at all now, I think he can still manually shift it though.

My brother called me and said that all the problems listed above start to act up when the speedometer all of the sudden stops working, then the ABS light comes on and the blazer can't shift. It has to be the VSS right?

im having the same problem
changed my vss and it was still there
my solution was going around checking every ground wire i could find and cleaning them, drove down the street and the lights were gone

Like stevo found, it could be a wiring problem or the sensor itself.

Well we changed the power brake booster because it was bad to begin with, and now the problem's gone, we didn't change anything else. The ABS light doesn't come on, and it's shifting fine again.

Very odd.. Glad it worked out for you. Hope it doesn't pop back up again.